Colored copolymers of cyclopentadiene and indole or pyrrole



United States Patent O This invention relates to relatively lowmolecular weight copolymers of cyclopentadiene and aminopolycues, and toa process for preparing the same.

P. V. French et al., in Proceedings of the Chemical Society, pages248-250, July 1960, describe highly colored homopolymers ofcyclopentadiene obtained by catalysts of the. colorless cyclopentadienepolymer with trichloroacetic acid. However, such polymers have beenfound.

tobe' unstable towards oxygen and protic solvents, and

hence are of limited practical value. I- have now made the discoverythat certain copolymers of cyclopentadiene can be prepared usingcationic catalysts such as hydrogenchloride, stannic chloride, aluminumchloride, and thelike, inprotic or aprotic solvents such as, forexample, methanol or chloroform, and that the protonated forms orhydrochloride salt forms of these copolymers are highly colored varyingbetween deep purple and bright red, and that they are remarkably stableboth as solids and inthe form of their neutral or acid solutions. Theyare soluble in either protic or aprotic solvents depending on theniodeof preparation, and are particularly useful as filter layers,antihalation and antistatic backings and overcoatings in photographicelements, as semi-conduca tors,l.ultra'-violet stabilizers, etc., ..dueto the absorption of various wavelengths as well as to their ioniccharacter. Solubilities can be adjusted, in case a carrier is used inthe coating compositions. However, both color and ionic character can bedischarged by the addition of base coin-pounds such as. alkalinephotographic developing agents which is a highly desirable property.

It is, accordingly, an object of the invention to provide highlycolored, protonated copolymers of cyclopen tadiene'that are stable as'crystallinesolids and in neutral or'acid solutions. Another object isto provide films and coatings of the same, especially for applicationsin the photographic art. Another object is to provide a process for prearing the said copolymers. Other objects will become apparenthcreiriafte'r.

In accordancewith the invention, I prepare the copolymers of theinvention by copolymerizing a mixture comprising from about 20 to 80% byweight of cyclopentatheme and from 80 to 20% by weight of anaminopolyene such as indole or pyrrole, in the presence of a cationicpolymerization catalyst such as stannic chloride (Such), hydrogenchloride gas, aluminum chloride, boron trifluoride, ferric chloride,etc., at a temperature of from about 50. C. to 100 C. In the case ofstannic chloride, a temperature range of from about 30 C. to 100 C. 'is'more efficacious, whereas with hydrogen chloride gas temperatures fromabout 50 C. to C. give the best results. Proportions of the aminopolyeneof less than 20% give undesirable copolymers which characterized bybecoming brittle on standing. Advantageously, the reaction-is carriedout in a solvent medium which may be protic or aprotic, but preferablyin chloroform. Other solvents that can be used as reaction mediumsinclude benzene, toluene or thylene dichloride. The deeply coloredcopolymer obtained may then be isolated by pouring the polymerizationreaction mixture into a nonsolvent for the copolymer such as acetone,ether, ligroin, petroleum, ether and similar solvents. The amount ofcatalyst employed can vary widely, but preferably from about 0.25 to25%, based on the total weight of mono- 3,247,172 Patented Apr. 19, 1906mers to be copolymerized. In general, more catalyst is required whereindole is the major polymerizable component. Mixtures of two or more ofthe catalysts can be used, if desired. While the polymerizations arepreferably carried out under normal atmospheric conditions, pressuressubstantially above or below atmospheric can also be employed. Themolecular weights of the copolymers produced as above described arerelatively lowranging from about 300 to 2000. The copolymeric productscontain about the same proportions of combined components as werepresent in the starting polymerization mixtures.

The following examples will serve to illustrate further the mannerofpracticing the invention.

Example 1 In a one-liter beaker are placed 66 g. (1 mole) ofcycloptentadiene and cc. of chloroform. With vi orous stirring 2 cc. ofa 5% by-weight solution of stannic chloride (SnCl in chloroform wasadded slowly. At this point, the temperature was 40 C.; then it roseslowly to 56 C. and the chloroform began to reflux gently.

When the temperature of the reaction mixture began to decrease, 20 g.(0.17 mole) of indole in 20 cc. of chloroform were added. The colorchanged to a pale yellow. The reaction mixture was stirred for 15minutes, then 2 cc. more of the catalyst solution were added, and themixture was refluxed for 15 minutes more with stirring. The polymerwhich formed precipitated out of solution as a blue-purple colored andgranular material, which was then filtered out, redissolved in methanoland reprecipitated into ligroin without loss of .color. It had anintrinsic viscosity of 0.2 in methanol in a concentration of 25 mg. per100 cc. of methanol. This corresponds to molecular weight of about 2000.Analysis of this pol- .ymeric product indicated that it was thehydrochloride salt of a copolymer of approximately 77% by weight ofrecurring cyclopentadiene units and 23% by weight of recurring indoleunits. On coating a solution of this copolymer in methanol, a thin,clear film was obtained which showed appreciable electric conductivitywhen measured between two parallel electrodes placed upon the film. Whenthe solution was applied as a backing layer onto a sheet of celluloseacetate photographic film, no static charge defects were noticeable inthe exposed and processed film. Also, all color had been discharged fromthis backing layer during the processing. The solution was also founduseful as an antistatic overcoating layer over gelatino-silver halideemulsion layers.

Example 2 In a one-liter beaker were placed 58 g. (0.5 mole) of indoleand 250 cc. of chloroform. Slowly a 50:50 solution of stannic chlorideand chloroform was added with stirring. After 8 cc. of the catalystsolution had been added, the reaction mixture became yellow and slightlycloudy. Then 16.5 g. (0.25 mole) of 1,3-cyclopentadiene were added.Another 32 cc. of the catalyst solution was then added slowly. Thetemperature rose slowly thereafter until at 58 C. a dark red polymerseparated out of the solution. This was separated, dissolved inmethanol, and precipitated'in ligroin. The process was repeated. Areddish-purple granular polymer was obtained which had an intrinsicviscosity of 0.07 in 25 mg. concentration in 100 cc. of methanol atroomtemperature corresponding to a molecular weight of about 300.Analysis indicated that this product was the hydrochloride salt of acopolymer of approximately 22% by weight of recurring cyclopentadieneunits and 78% by weight of recurring indole units. The properties andutility of this copolymer were generally the same as those shown for theproduct of Example 1.

Example 3 In a one-liter beaker were placed 67 g. (1 mole) of pyrroleand 200 cc. of chloroform. The temperature was then adjusted to 40 C. inan actone-Dry Ice (solid carbon dioxide) bath. The mixture was stirredby hand while hydrogen chloride gas bubbled in slowly. The temperaturewas maintained between 40 C. and 33 C. for one hour, the solutionturning pale yellow and slightly viscous.

Then 66 g. (1 mole) of 1,3-cyclopentadiene mixed in 81 cc. of chloroformwas added a few ccs. at a time with stirring, while maintainingtemperature below -33 C. The addition required one hour to complete.Hydrogen chloride gas was then bubbled in for another two hours keepingthe temperature constant at -33 C.

The solution turned pink and more viscous. It was then poured intoligroin to drive off the hydrogen chloride gas and to precipitate thepolymer. This turned dark red on standing overnight and was thendissolved in methanol and precipitated in ether. This procedure wasrepeated several times. A red powdery material was finally obtained.Analysis indicated that this material was the hydrochloride salt of acopolymer consisting of approximately 50% by weight of recurringcyclopentadiene units and 50% by weight of recurring pyrrole units. Ithad an intrinsic viscosity of 0.04 as measured in 25 mg. solutionthereof in 100 cc. methanol at room temperature, corresponding tomolecular weight of about 300. Coatings of this copolymer were alsouseful as antistatic backing layers on photographic films.

Example 4 In a one-liter beaker were mixed 66 g. (1 mole) of 1,3-cyclopentadiene and 200 cc. of cholorform, and the temperature adjustedto -40 C. in a Dry Ice bath.

Hydrogen chloride gas was then bubbled in and 67 g. (1 mole) of pyrrolewas added in 3 cc. portions over a period of one and one-half hours. Thetemperature rose with each addition and the color of the solutionchanged finally to orange-red color.

The reaction mixture was allowed to come to room temperature and leftstanding for 65 hours. A hard, dark red, chloroform insoluble polymerprecipitated out of solution. This was dissolved in methanol andprecipitated in acetone, followed by extraction of the precipitatedpolymer with a 50:50 chloroform-acetone mixture over a period of 5 days.A dark red polymer was obtained finally which was identified as thehydrochloride salt of a copolymer of approximately 50% by weight ofrecurring cyclopentadiene units and 50% by weight of recurring pyrroleunits. It had an intrinsic viscosity of 0.08 as measured in 25 mg.solution thereof in methanol at 20 C., corresponding to a molecularweight of approximately 350. Coatings from 5% methanol solutions thereofproduced thin continuous layers which were conductive and reduced staticcharge buildup when applied as backings on photographic films.

While the preceding examples have described copolymers of the inventionin just certain proportions of components, it will be understood thatthe procedures of the examples are equally applicable for thepreparation of any protonated copolymers of the invention coming Withinthe specified limits of from 20-80% by weight of cyclopentadiene unitsand from 8020% by weight of either indole units or pyrrole units. Also,it should be further understood that any mixtures of indole and pyrrolecan be used as comonomers provided only that their total weight is notless than 20% and not more than 80% of the total weight of the monomersto be copolymerized. These protonated copolymers likewise on coatinginto films or antistatic layers on photographic films become colorlessin the basic processing solutions. All of the protonated, coloredcopolymers of the invention, as

1. A solid copolymer consisting essentially of from 2080% by weight ofrecurring cyclopentadiene units and from 20% by weight of recurringunits selected from the group consisting of indole units, pyrrole unitsand a mixture of indole and pyrrole units, the said copolymer being inthe halide salt form and having a molecular weight of from 300 to 2000.

2. A solid copolymer consisting essentially of from 20-80% by weight ofrecurring cyclopentadiene units and fronr80-20% by weight of recurringindole units, the said copolymer being in the halide salt form andhaving a molecular weight of from 300 to 2000.

3. A solid copoiymer consisting essentially of from 2080% by weight ofrecurring cyclopentadiene units and from 8020% by weight of recurringpyrrole units, the said copolymer being in the halide salt form andhaving a molecular weight of from 300 to 2000.

4. The solid hydrochloride salt of a copolymer consisting essentially offrom 2080% by weight of recurring cyclopentadiene units and from 8020%by weight of recurring units selected from the group consisting ofindole units, pyrrole units and a mixture of indole and pyrrole units,the said copolymeric salt having a molecular weight of from 300 to 2000.

5. The solid hydrochloride salt of a copolymer consisting essentially offrom 2080% by weight of recurring cyclopentadiene units and from 8020%by weight of recurring indole units, the said copolymeric salt having amolecular Weight of from 300 to 2000.

6. The solid hydrochloride salt of a copolymer consisting essentially offrom 2080% by weight of recurring cyclopentadiene units and from 8020%by weight of recurring pyrrole units, the said copolymeric salt having amolecular weight of from 300 to 2000.

7. A process for preparing a solid, protonated copolymer which comprisescontacting a mixture consisting essentially of from 2080% by weightcyclopentadiene and 8020% by weight of a monomer selected from the groupconsisting of indole, pyrrole and a mixture of indole and pyrrole with acationic hydrogen halide forming polymerization catalyst at from -50 toC.

8. The process according to claim 7 wherein the said monomer is indoleand wherein the said cationic polymmerization catalyst is stannicchloride.

9. The process according to claim 7 wherein the said monomer is pyrroleand wherein the said cationic polymerization catalyst is stannicchloride.

10. The process according to claim 7 wherein the said monomer is indoleand the said cationic polymerization.

2,521,359 2,529,316 11/1950 Smyersetal 26082.1

OTHER REFERENCES Brown et al., Chem. Soc. Jour. (London), Pt, 3 (1957),pp. 3608-3611.

JOSEPH L. SCHOFER, Primary Examiner.

9/1950 Garber 260--82.1

1. A SOLID COPOLYMER CONSISTING ESSENTIALLY OF FROM 20-80% BY WEIGHT OFRECURRING CYCLOPENTADIENE UNITS AND FROM 80-20% BY WEIGHT OF RECURRINGUNITS SELECTED FROM THE GROUP CONSISTING OF INDOLE UNITS, PYRROLE UNITSAND A MIXTURE OF INDOLE AND PYRROLE UNITS, THE SAID COPOLYMER BEING INTHE HALIDE SALT FORM AND HAVING A MOLECULAR WEIGHT OF FROM 300 TO 2000.